Effect of heat treatment on the wet abrasion resistance of WC-10Co4Cr coatings deposited onto stainless steel by HVOF

Heat treatments were carried out at 350, 450, 550 and 650 degrees C on WC-10Co4Cr coatings deposited by High-Velocity Oxy-Fuel (HVOF) onto AISI 420 stainless steel substrate in order to study their influence on the abrasive wear resistance of the coatings. The thickness and microhardness of the coatings were measured while the microstructure was analysed with the aid of OM, SEM and XRD techniques. The X-ray diffraction results revealed the presence of W2C phase in the as-sprayed coatings, and WO3 and CoWO4 phases after the heat treatments. No significant degradation of the microstructure was observed in coatings treated at 350 degrees C compared with the as-sprayed coatings. Coatings treated at temperatures above 450 degrees C, on the other hand, showed significant changes related to density, microstructure and surface hardness. The coatings treated at 350 degrees C showed the best wear resistance, while the coatings treated at 550 degrees C presented the worst performance due to microstructural defects related to oxidation processes. [GRAPHICS]